Superconductivity due to coulomb interactions

M. Curie

Soh Koike, Yamaji K.

D. Schmeltzer

Takashi Yanagisawa

It is important to understand the mechanism of high-temperature superconductivity. It is obvious that the interaction with large energy scale is responsible for high critical temperature T c . The Coulomb interaction is one of candidates that bring about high-temperature superconductivity because its characteristic energy is of the order of eV. There have been many works for the Hubbard model including three-band d-p model with the on-site Coulomb repulsion to investigate a possibility of high-temperature superconductivity. It is, of course, not trivial whether the on-site Coulomb interaction leads to a pairing interaction between two electrons. We argue that high-temperature superconductivity is possible in the strongly correlated region by using the variational Monte Carlo method for the two-dimensional t-U-J-V model. The exchange interaction J and the nearest-neighbour attractive interaction V cooperate with U and will act to enhance the critical temperature.

Satoshi Yamazaki, Shintaro Hoshino, Yoshio Kuramoto

Superconducting transition temperature is studied in the strong-coupling region of the Holstein-Hubbard model that includes both electron-phonon and Coulomb interactions.By combining the dynamical mean field theory with the continuous-time quantum Monte Carlo method, transition temperature is derived numerically.Without Coulomb interaction, our calculation reproduces analytic expressions of the transition temperature for weak and strong coupling limits of electron-phonon interaction.When electron-phonon coupling is strong enough, Coulomb repulsion enhances superconductivity, in contrast to the weak coupling case.The enhancement is due to coherent motion of superconducting pairs that reduce the Coulomb repulsive energy of almost localized electrons.

Valerii Vladimirovich Val'kov, T. A. Val’kova, Vitaly A. Mitskan

The concentration dependence of the position of nodal points of a superconducting order parameter is investigated using the t – J – V model for a triangular lattice with regard to the exchange and Coulomb interactions in two coordination spheres. The conditions for a topological quantum transition are established.